This invention relates to a heat pump that is operable in both a cooling and a heating mode, and wherein a four-way valve utilized to switch between cooling and heating modes and provide a bypass, or an unloader function.
Refrigerant systems are utilized to control the temperature and humidity of air in various indoor environments to be conditioned. In a typical refrigerant system operating in the cooling mode, a refrigerant is compressed in a compressor and delivered to a condenser (or an outdoor heat exchanger in this case). In the condenser, heat is exchanged between outside ambient air and the refrigerant. From the condenser, the refrigerant passes to an expansion device, at which the refrigerant is expanded to a lower pressure and temperature, and then to an evaporator (or an indoor heat exchanger). In the evaporator, heat is exchanged between the refrigerant and the indoor air, to condition the indoor air. When the refrigerant system is operating, the evaporator cools the air that is being supplied to the indoor environment.
The above description is of a refrigerant system being utilized in the cooling mode of operation. In the heating mode, the refrigerant flow through the system is essentially reversed. The indoor heat exchanger becomes the condenser and releases heat into the environment to be conditioned (heated in this case) and the outdoor heat exchanger serves the purpose of the evaporator and exchangers heat with a relatively cold outdoor air. Heat pumps are known as the systems that can reverse the refrigerant flow through the refrigerant cycle, in order to operate in both heating and cooling modes. This is usually achieved by incorporating a four-way reversing valve (or an equivalent device) into the system design, with the valve located downstream of the compressor discharge port. The four-way reversing valve selectively directs the refrigerant flow through the indoor or outdoor heat exchanger when the system is in the heating or cooling mode of operation, respectively. Furthermore, if the expansion device cannot handle the reversed flow, than a pair of expansion devices, each along with a check valve, can be employed instead.
Another aspect of controlling the capacity in a refrigerant cycle such as a heat pump is the ability to selectively reduce capacity. So-called “unloader” valves or bypass valves are utilized to selectively bypass at least a portion of the compressed refrigerant from the compressor discharge back toward the compressor suction. The terms bypass and unloader are used synonymously in this application.
While the bypass valves are an important and widely utilized capacity control features, they do require the inclusion of a separate valve and associated piping. It would be desirable to eliminate the necessity of a separate valve and associated piping.